CN116348565B

CN116348565B - Adhesive composition and adhesive tape

Info

Publication number: CN116348565B
Application number: CN202180072629.5A
Authority: CN
Inventors: 土屋靖史; 冈村菖子
Original assignee: Teraoka Seisakusho Co Ltd
Current assignee: Teraoka Seisakusho Co Ltd
Priority date: 2021-03-31
Filing date: 2021-03-31
Publication date: 2024-03-12
Anticipated expiration: 2041-03-31
Also published as: KR20230054488A; JPWO2022208814A1; CN116348565A; KR102624251B1; TW202305078A; WO2022208814A1; TWI814280B; JP7072735B1

Abstract

In order to provide a rubber-based adhesive composition having excellent adhesion to various adherends represented by metals, resins and coating materials, high-temperature retention and re-peelability, and an adhesive tape using the rubber-based adhesive composition, the following adhesive composition is used, and is characterized in that the adhesive composition comprises a natural rubber, a crosslinking agent, a tackifier and a crosslinking regulator, the adhesive composition has a minimum loss tangent temperature after curing of 78.7 ℃ to 0.20, and a maximum loss tangent temperature of 25.0 ℃ to 1.15, and the adhesive tape is produced in which an adhesive layer (12) is formed on at least one surface of a sheet-like substrate (11).

Description

Adhesive composition and adhesive tape

Technical Field

The present invention relates to an adhesive composition using a natural rubber as a main component, and relates to an adhesive composition which has a high degree of crosslinking, excellent cohesiveness and self-adhesive surface adhesiveness, and excellent adhesive force, high-temperature retention, and re-peelability to various adherends represented by metals, resins, and coating materials.

The present invention also relates to an adhesive tape which uses the adhesive composition and has a strong fixing force required in the production, assembly and transportation of an article, and which is suitable for temporary fixing that is easy to peel with little contamination of an adherend in the case of re-peeling.

Background

Industrial products such as information equipment, office equipment, home electric appliances, and interior decoration are manufactured, and an adhesive tape is directly attached to an article for the purpose of masking, reinforcing, protecting, identifying, or preventing breakage during transportation after manufacture, or assisting package, and is peeled off after the purpose is achieved. Therefore, such a pressure-sensitive adhesive tape for temporary fixation is required to have opposite properties such as excellent fixing force (adhesive force, high-temperature retention property) to an adherend and less contamination (re-peelability) to the adherend when peeling (also referred to as re-peeling) is performed.

In order to facilitate peeling of the tape and further improve the re-peelability, it is required that the tape end, which is the handle at the time of re-peeling of the tape, be maintained in a state of being folded back to the paste surface side (self-adhesive surface adhesion).

As an adhesive suitable for the temporary fixing adhesive tape used for such a purpose, acrylic-based and rubber-based adhesives are exemplified from the standpoint of performance and price.

Patent document 1 describes that the pressure-sensitive adhesive layer is obtained by curing an isoprene rubber and a tackifier with a curing agent in the presence of a zirconium compound. Patent document 2 describes that a primer layer containing a composition containing a rubber component containing a natural rubber obtained by polymerizing methyl methacrylate, an isocyanate compound, and an aminoethylated acrylic resin is provided between a rubber-based pressure-sensitive adhesive layer and a base material. Patent document 3 describes an adhesive sheet comprising a layer containing a solid adhesive composition obtained by adding a tackifier to a rubbery polymer and crosslinking the resultant polymer with an isocyanate-based crosslinking agent.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2014-034582

Patent document 2: japanese patent application laid-open No. 2014-240484

Patent document 3: japanese patent laid-open No. 2001-181596

Disclosure of Invention

Problems to be solved by the invention

Patent document 1 considers that the cohesive force of the adhesive is improved by using an organozirconium compound as the zirconium compound and curing with an isocyanate-based curing agent as the curing agent, but the gel fraction is low (17 to 30%) even when an organozirconium compound is used, and the measurement conditions are mild, and therefore, the high-temperature retention and the residual tackiness targeted by the present invention are expected to be poor.

In patent document 2, as a preferred embodiment, the pressure-sensitive adhesive layer contains, in combination with the above-mentioned specific primer layer, 50 to 80 parts by weight of a natural rubber and 20 to 45 parts by weight of an elastomer containing an isoprene rubber having a peroxide in the molecule, 50 to 100 parts by weight of a tackifying resin, and 0.1 to 15 parts by weight of a crosslinking agent, and has a strong adhesive force, and contamination of the adherend, such as a residual adhesive, when the tape is peeled off is remarkably suppressed. It is also considered that the addition of a liquid isoprene rubber having a peroxide in the molecule makes it possible to crosslink the natural rubber under a storage environment at normal temperature and humidity without using sulfur or peroxide which is generally used for crosslinking (vulcanization) and without requiring maintenance at 120 ℃. It is also considered that epoxy resins, isocyanate resins, and the like are described as being used as the crosslinking agent, but epoxy resins are preferable (paragraph 0023). In the examples, isocyanate compounds were used for the primer layer, but the crosslinking agent for the adhesive layer was an epoxy system, and the adhesive layer was crosslinked by using not only pure natural rubber but also liquid isoprene rubber having peroxide in the molecule. Since the qualification level of the gel fraction is set to be as low as 20% and the qualification level of the retention force measurement condition is also low, it is difficult to say that the retention force is sufficient as the object of the present invention.

The adhesive composition of patent document 3 is a solid-type composition obtained by adding a tackifier and an isocyanate-based crosslinking agent to a rubbery polymer containing natural rubber in the absence of a solvent, kneading the mixture by heating at 80 to 120 ℃ and simultaneously crosslinking the mixture. The heat kneading method was studied, and it was considered that even a solid type using an isocyanate-based crosslinking agent could achieve extremely weak moderate crosslinking, and the cohesive force could be improved while maintaining the adhesive force, and even if a small amount of the crosslinking agent was added, the crosslinking agent could be uniformly dispersed without causing a decrease in molecular weight. However, in patent document 3, although the adhesion test by peeling was performed at 23 ℃ and the retention test by a load of 2kg was performed at 40 ℃, the characteristics at high temperature were not further evaluated.

In addition, conventionally, there has been studied an adhesive tape for temporarily fixing an article using an acrylic adhesive, which is excellent in fixing force and cohesive force, and which is obtained by using an acrylic adhesive, and in the case of an acrylic adhesive, the self-adhesive surface adhesion is insufficient, and the adhesive force to metals and glass is high, and there is a concern that the adherend is contaminated at the time of re-peeling.

The purpose of the present invention is to provide a rubber-based adhesive composition which has excellent adhesive force, high-temperature retention and low contamination to various adherends represented by metals, resins and coating materials.

Further, an object of the present invention is to provide a temporary fixing adhesive tape which uses a rubber-based adhesive, is less contaminated by an adherend after re-peeling even when exposed to a high temperature and high humidity environment during the production, assembly and transportation of an article, and can be held in a state where the tape end, which is a handle when re-peeling the tape, is folded back to the paste surface side, and therefore is excellent in peeling easiness and has excellent adhesive force, and therefore can sufficiently perform temporary fixing of an article even when the width is narrow.

Means for solving the problems

The adhesive composition according to one embodiment of the present invention is characterized in that it is an adhesive composition comprising a natural rubber, a crosslinking agent, a tackifier and a crosslinking regulator, the adhesive composition having a minimum loss tangent temperature after curing of 78.7 ℃ or higher and a minimum value of 0.20 or lower, and the maximum loss tangent temperature of 25.0 ℃ or lower and a maximum value of 1.15 or lower.

In addition, another embodiment of the pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition on at least one surface of a sheet-like substrate.

Effects of the invention

According to one embodiment of the present invention, there is provided a rubber-based adhesive composition having excellent adhesion to various adherends such as metal, resin and coating materials, high-temperature retention and re-peelability (low contamination).

In addition, according to another aspect of the present invention, there is provided an adhesive tape for temporary fixation which has a strong fixing force required in the production, assembly and transportation of an article, is less contaminated with an adherend at the time of re-peeling, and is suitable for easy peeling.

Drawings

Fig. 1 is a diagram showing an example of the structure of an adhesive tape according to an embodiment.

Fig. 2 is a diagram showing another configuration example of the adhesive tape according to the embodiment.

Detailed Description

An adhesive composition according to an embodiment of the present invention will be described.

The adhesive composition of the present embodiment is characterized by comprising a natural rubber, a crosslinking agent, a tackifier and a crosslinking regulator, wherein the minimum temperature of the loss tangent after curing of the adhesive composition is 78.7 ℃ or higher and 0.20 or lower, and the maximum temperature of the loss tangent is 25.0 ℃ or lower and 1.15 or lower.

< loss tangent >)

Loss tangent (loss modulus (G ")/storage modulus (G')=loss tangent (tan δ)) refers to the degree of contribution of loss modulus (viscosity) to storage modulus (elasticity).

The minimum loss tangent temperature of the adhesive composition after curing is 78.7 ℃ or higher: the minimum value of the degree of contribution of loss modulus (tackiness) is small, and the temperature at which the cured product containing the adhesive composition has a prescribed hardness is high, that is, the adhesive layer containing the adhesive composition maintains a moderate hardness even at a relatively high temperature. If the minimum temperature of the loss tangent is less than 78.7 ℃, the holding power at high temperature is poor.

The minimum value of loss tangent after curing of the adhesive composition is 0.20 or below: the cured product (adhesive layer) of the adhesive composition is less likely to become excessively soft and less likely to flow.

Further, the maximum temperature of the loss tangent means a glass transition temperature, and the maximum temperature of the loss tangent of the adhesive composition is 25.0 ℃ or lower: the cured product of the adhesive composition has a low glass transition temperature and maintains flexibility moderately even at low temperatures.

The maximum value of the loss tangent is represented by the peel resistance, and the maximum value of the loss tangent of the cured product of the adhesive composition is represented by 1.15 or less: the pressure-sensitive adhesive composition has a low peel resistance when used as a pressure-sensitive adhesive layer, and pressure-sensitive adhesive tapes using the composition are easily peeled.

The respective components will be described.

< Natural rubber >)

The natural rubber is obtained by coagulating and drying natural rubber latex which is sap of a rubber tree, and is a substance containing cis-1, 4-polyisoprene as a main component.

The structure of a natural rubber molecule is said to be a structure in which one end of a cis-1, 4-isoprene unit is constituted by a protein end, a phospholipid is bonded to the other end, and a long-chain fatty acid is further bonded to the phospholipid end.

The natural rubber contains 3 to 4 mass% of a non-rubber component such as protein and lipid.

Therefore, the natural rubber can be easily crosslinked and cured by a crosslinking agent described later. Since the adhesive composition of the present invention is crosslinked and cured, the crosslinked product is also referred to as a cured product.

Examples of the classification of the natural rubber used include standard Malaysia rubber (Standard Malaysian Rubber) (SMR), standard Indonesia rubber (Standard Indonesian Rubber) (SIR), tobacco flake Rubber (RSS) Nos. 1 to 6, and crumpled rubber Nos. 1 to 3.

In addition, in general, the molecular weight of the natural rubber which is not plasticated is extremely high, and if the molecular weight of the natural rubber is too high, the plasticity is high, and in the case of the adhesive composition, flexibility is poor, and in some cases, the proper adhesive properties cannot be obtained.

Therefore, it is necessary to adjust the plasticity by mechanically kneading the natural rubber in advance by a pressure kneader, a Banbury mixer, an open mill, or the like to appropriately reduce the molecular weight of the natural rubber.

In particular, as the plasticity of the natural rubber used in the adhesive composition of the present invention, the Mooney viscosity ML ₁₊₄ The temperature (100 ℃) is preferably 10 to 85, more preferably 20 to 35. If the plasticity is too low or too high, there are cases where it is not possible to obtain both excellent adhesion required for temporary fixing of an article and high cohesive forceAnd an adhesive tape.

< crosslinker >

As a method for crosslinking natural rubber, a method of vulcanization treatment using a vulcanizing agent and a crosslinking method based on a reaction between functional groups are known.

In the vulcanization system, a vulcanizing agent such as a sulfur-based, thiuram-based, or quinone-based agent acts on unsaturated bonds contained in the molecular main chain of the natural rubber, and a reaction mechanism for directly crosslinking polymers to each other is adopted, so that a dense and strong crosslinking with a high cohesive force can be achieved.

However, since the crosslinking mechanism is direct and strong, the tackiness drastically decreases with an increase in the vulcanization degree, and the adhesive strength also significantly decreases. In addition, sulfur components are known as components causing corrosion of metals, and are not preferable for temporary fixation purposes for direct adhesion to various adherends typified by metals, resins, and coating materials.

On the other hand, in the crosslinking system based on the reaction between functional groups, a polyfunctional compound having a functional group reactive with a functional group such as a hydroxyl group or a carboxyl group which is sometimes introduced into a molecular side chain during the production of a natural rubber, or a functional group of a non-rubber component such as a protein or a lipid which is mixed into the natural rubber in an amount of about 3 to 4 mass%, is added to crosslink based on the reaction between functional groups.

In this method, as the crosslinking agent, for example, a crosslinking agent containing an isocyanate compound, an epoxy compound, an oxazoline compound, an aziridine compound, a butylated melamine compound, or the like is known.

Further, the non-sulfur-based crosslinking agent other than the vulcanizing agent does not contain sulfur components which are liable to cause corrosion of metals, and is therefore more preferable for temporary fixation purposes of being directly adhered to various adherends typified by metals, resins, and coating materials.

The present inventors have found that if natural rubber can be crosslinked flexibly and densely, a rubber-based adhesive having excellent adhesion required for temporary fixing of an article, high cohesive force, high-temperature retention, and excellent re-peeling property can be provided. In order to achieve the above object, studies have been made on crosslinking agents which are characterized by being non-sulfur-based crosslinking agents and capable of high crosslinking, based on the above-described technical knowledge, with trial and error.

As a result, the present inventors have found that, by using a crosslinking agent containing an isocyanate compound as a main component among the above crosslinking agents, natural rubber can be crosslinked flexibly and densely as an adhesive composition having excellent adhesive force required for temporary fixation of an article.

Further, it has been found that the use of a crosslinking agent containing at least 1 compound selected from isocyanate compounds containing a diphenylmethane diisocyanate structure (polymeric MDI) as a main component in the isocyanate compound can provide a rubber-based adhesive having excellent adhesion to various adherends, high-temperature retention and re-peelability.

That is, as the crosslinking agent used in the adhesive composition and the adhesive sheet of the present invention, a crosslinking agent containing an isocyanate compound as a main component, particularly a crosslinking agent containing at least 1 compound selected from isocyanate compounds containing a diphenylmethane diisocyanate structure as a main component, can be preferably used.

The crosslinking agent may be used by adding 1 to 15 parts by mass, preferably 2.5 to 10 parts by mass, to 100 parts by mass of the natural rubber. When the amount is within this range, the above-mentioned characteristics of loss tangent can be satisfied.

< tackifier >)

In the adhesive composition of the present embodiment, as the tackifier, a tackifier resin having good compatibility with natural rubber can be used, and in particular, at least 1 resin selected from petroleum resins, terpene resins, rosin resins, and other resins having a softening point of 125 ℃ or higher can be used. Particularly preferred is a petroleum resin (saturated aliphatic hydrocarbon resin) having a softening point of 125℃or higher. Such a tackifier may be used by adding 50 to 100 parts by mass, preferably 60 to 90 parts by mass, to 100 parts by mass of natural rubber.

When a tackifier resin having a softening point of less than 125 ℃ is used as a tackifier, an adhesive composition and an adhesive tape having excellent adhesive force, high-temperature retention property and re-releasability required for temporary fixing of articles may not be obtained.

In addition, when the amount of the tackifier added is too large or too small, the adhesive composition and the adhesive tape having the above-mentioned physical properties may not be obtained.

< crosslinking modifier >

In the adhesive composition of the present embodiment, the degree of crosslinking (gelation degree) of the composition is adjusted by using a crosslinking regulator. This is used for the purpose of achieving a moderately soft and dense crosslinking reaction within a range that allows both excellent adhesion and high cohesion and high temperature retention of the adhesive composition. In particular, in the present invention, a compound that inhibits the reaction of an isocyanate compound as a crosslinking agent with hydroxyl groups or the like of a natural rubber to some extent is used as a crosslinking regulator.

The adhesive composition of the present embodiment may be used by adding at least 1 compound selected from the group consisting of a hindered phenol compound, a phosphorus compound, a metal compound, a benzotriazole compound, a triazine compound, a hindered amine compound, and the like as a crosslinking regulator.

Specific examples of the hindered phenol compound include pentaerythritol tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], 2' -thiodiethyl bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], N-octadecyl 3- (4 ' -hydroxy-3 ',5' -di-tert-butylphenyl) propionate, N ' - (hexane-1, 6-diyl) bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ], octyl-3, 5-di-tert-butyl-4-hydroxy-hydrocinnamic acid, 2,4, 6-tris (3 ',5' -di-tert-butyl-4 ' -hydroxybenzyl) mesitylene, 2, 4-bis (octylthiomethyl) -6-methylphenol, bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate ] [ ethylenebis (oxyethylene) ] ester, 1, 6-hexanediol bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], 1, 5-tris (3, 5-di-tert-butyl-4-hydroxy-4-hydroxyphenyl) propionate ], 1, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) s, 1, 6-tris (3, 6-di-tert-butyl-4 ' -hydroxybenzyl) s-m-trimethylbenzene, 2, 4-tris (3, 4-hydroxybenzyl) s) -tris (3, 5-hydroxy-4-t-butylphenyl) propionate, and the like.

Further, as the phosphorus compound, specifically, tris (2, 4-di-t-butylphenyl) phosphite is given. Specific examples of the metal compound include 3- (3, 5-di-t-butyl-4-hydroxyphenyl) -N' - [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionyl ] propionyl hydrazine. Specific examples of the benzotriazole-based compound include 4-methyl-2- (2H-benzotriazol-2-yl) phenol, 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol, 2- (5-chloro-2H-benzotriazol-2-yl) -6- (1, 1-dimethylethyl) -4-methylphenol, 2' -methylenebis [6- (2H-benzotriazol-2-yl) -4- (1, 3-tetramethylbutyl) phenol ], and benzotriazolyldodecyl-p-cresol. Specific examples of the triazine compound include 2- (4, 6-diphenyl-1, 3, 5-triazin-2-yl) -5- (hexyloxy) phenol. As the hindered amine-based compound, specifically, examples thereof include poly- [6- [ (1, 3-tetramethylbutyl) amino ] -s-triazine-2, 4-diyl ] - [ (2, 6-tetramethyl-4-piperidinyl) imino ] -hexamethylene- [ (2, 6-tetramethyl-4-piperidinyl) imino ] ]. Dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2, 6-tetramethyl-4-piperidine polycondensate dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2, 6-tetramethyl-4-piperidine polycondensate. Wherein the preferable crosslinking modifier is at least 1 compound selected from the group consisting of hindered phenol compounds.

The amount of the crosslinking regulator is not particularly set, but when the amount of the crosslinking regulator is too large, the natural rubber cannot be flexibly and densely crosslinked, and an adhesive composition and an adhesive tape which are excellent in adhesion and high in cohesive force and high in high-temperature retention required for temporary fixing of an article cannot be obtained in some cases. If the amount is too small, the effect of adding the crosslinking regulator may not be sufficiently exhibited. The amount is preferably 1.0 to 5.0 parts by mass, more preferably 2.0 to 4.0 parts by mass, based on 100 parts by mass of the natural rubber.

< other additives >)

In the adhesive composition, if necessary, 1 or 2 or more of an inorganic filler, an organic filler such as a resin, a softener, a plasticizer, a surfactant, a coupling agent, a colorant, a preservative, a heat stabilizer, a light stabilizer, and the like may be further added within a range that does not impair the above physical properties.

In the present specification, "adhesive composition" means both a mixture of components before crosslinking and a composition after crosslinking, and in the following adhesive tape, "adhesive layer" includes the adhesive composition, in which case "adhesive composition" means the composition after crosslinking. In addition, a state in which the adhesive layer is dissolved or dispersed in a solvent, and a dried product from which the solvent is removed are sometimes referred to as an "adhesive composition".

[ adhesive tape ]

The pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape comprising a sheet-like substrate and, formed on at least one surface thereof, a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition. For example, the adhesive tape may be a single-sided adhesive tape in which an adhesive layer 12 containing the adhesive composition is provided on one side of a substrate 11 as shown in fig. 1, or a double-sided adhesive tape in which the adhesive composition is used in at least one or both of an adhesive layer 22 and an adhesive layer 23 provided on both sides of a substrate 21 as shown in fig. 2.

The adhesive layer 12 in fig. 1, the adhesive layer 22 and/or 23 in fig. 2 can be formed by applying a coating liquid in which the adhesive composition is dissolved or dispersed in a suitable solvent to the sheet-like base material 11 or 12 using a roll coater, a die coater, or the like, or by coextruding the adhesive composition with these base materials without using a solvent. Preferably by: a coating liquid is prepared by mixing and dissolving natural rubber, a crosslinking agent, a tackifier, a crosslinking regulator, and other additives in a solvent such as toluene, and the coating liquid is applied to one side of the substrate 11, one side or both sides of the substrate 21, using a coater or the like so that the thickness of the dried adhesive layer is uniform, and then the applied adhesive composition is dried and cured at a predetermined temperature.

The thickness of the adhesive layer after drying and curing is not particularly limited, and may be any thickness, and is usually about 10 to 70 μm, preferably 25 to 50 μm, as long as the excellent adhesive force, self-adhesive surface adhesiveness, cohesive force and high-temperature retention required for temporary fixing of the article are exhibited.

In addition, the surface (surface 11A) of the sheet-like substrate 11 facing the adhesive layer 12 in fig. 1 may be subjected to surface treatment such as corona discharge treatment, or provided with a primer layer, or both, as necessary, whereby the adhesion of the adhesive layer 12 to the substrate 11 can be improved. In addition, by providing a release layer as necessary on the surface 11B of the sheet-like substrate 11 opposite to the surface 11A in fig. 1, the adhesive composition can be prevented from adhering to the surface 11B of the substrate 11 when the adhesive tape of this embodiment is wound into a roll, and the ease of rewinding (pulling-out) can be maintained.

In addition, the adhesion between the pressure-sensitive adhesive layer 22 or the pressure-sensitive adhesive layer 23 and the substrate 21 can be improved by performing surface treatment such as corona discharge treatment, providing an undercoat layer, or both of the two surfaces (21A and 21B) of the sheet-like substrate 21 in fig. 2.

< sheet-like substrate >)

The type of the sheet-like base material is not particularly limited, and may be a commonly used nonwoven material such as a known film, foam, woven fabric, knitted fabric, paper, or the like, as long as it is in a sheet form.

Among them, a film base material made of a resin is preferable, and examples of the resin material include Polyethylene (PE), polypropylene (PP), stretched polypropylene (OPP), polyester, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyethylene naphthalate (PEN), polyphenylene sulfide, ethylene-vinyl acetate copolymer (EVA), and the like, and a blend thereof. In the case of a film containing such a synthetic resin, the film is excellent in mechanical strength, free from contamination by an adherend, and preferable as an adhesive tape for temporary fixation used in the production, assembly and transportation of an article.

The thickness of the sheet-like base material may be appropriately selected and used within a range capable of maintaining the strength required for the pressure-sensitive adhesive tape, and is preferably 10 to 300. Mu.m, more preferably 10 to 100. Mu.m, and still more preferably 12 to 75. Mu.m. In particular, when the thickness is in the range, a polyethylene terephthalate (PET) film is excellent in mechanical strength, exhibits high fixing force, and does not cause contamination of an adherend, and is more preferable as an adhesive tape for temporary fixing used in the production, assembly and transportation of articles.

< primer >

The primer used for the primer layer is not particularly limited, and any primer may be used as long as the effect thereof is exhibited. In particular, if the primer layer has a functional group capable of reacting with a functional group of a compound contained in the adhesive layer, the reaction proceeds toward the primer layer even when the adhesive layer is crosslinked, and the adhesion to the substrate can be improved. The adhesion amount or unit area weight of the dried undercoat layer is usually 0.2 to 2g/m ² Preferably 0.4 to 1.2g/m ² 。

< mold Release agent >

When the adhesive layer 12 is formed on one surface 11A of the base material 11 and wound into a roll shape as shown in fig. 1, the adhesive layer contacts the other surface 11B of the base material. In order to optimize the pullout from the roller, a release layer is preferably formed in advance on the surface 11B. The release agent used in the release layer is not particularly limited, and any release agent may be used as long as it exerts its effect. For example, silicone resins, long-chain alkyl vinyl monomer polymers, fluorinated alkyl vinyl monomer polymers, polyvinyl alcohol urethanes, and the like are known. Among them, silicone resins are excellent in the property of improving the peeling property of the substrate surface. The adhesion amount or unit area weight of the dried release layer is usually 0.2 to 2g/m ² Preferably 0.4 to 1.2g/m ² 。

< release sheet >

In the case of the double-sided adhesive tape shown in fig. 2, it is preferable in terms of operability that the release sheet is laminated on the outer surface of the adhesive layer in advance so as to be releasable. In the case of winding into a roll, the release sheet may be wound so as to be sandwiched between the adhesive layer 22 and the adhesive layer 23. Since the release sheet does not need to have a high strength, a release sheet obtained by subjecting one or both surfaces of a sheet to the release treatment as described above can be used.

Examples

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the examples.

In the following description, "parts" means "parts by mass".

The materials used in examples and comparative examples are as follows. The physical property values of the respective materials were the manufacturer catalog values.

A base material: PET film (thickness 38 μm)

Natural rubber: rubber with cockle

(Mooney viscosity grades using table-borne)

Crosslinking agent:

a trade name "Millionate MR-200",

polymeric MDI manufactured by Tosoh

B trade name "corona L-45E",

modified polyisocyanate prepared from Tosoh

C trade name "E-5C", manufactured by comprehensive chemical Co-production, epoxy crosslinking agent

D trade name "Vulkacit Thiuram/C", LANXESS Co., ltd,

thiuram vulcanizing agent (tetramethyl thiuram disulfide)

Tackifier:

a trade name "Pensel D-135", manufactured by the chemical industry of Sichuan,

polymerized rosin ester with softening point of 130-140 DEG C

B trade name "Arkon P-140", manufactured by the chemical industry of Sichuan,

petroleum resin with softening point 140 + -5 DEG C

C trade name "Arkon P-100", manufactured by the chemical industry of Sichuan,

petroleum resin with softening point of 100+ -5 DEG C

Crosslinking regulator: trade name "Irganox 1010", manufactured by BASF Japan,

(hindered phenol-based Compound)

Examples 1 to 8, reference example 1 and comparative examples 1 to 12

Adhesive compositions were prepared in accordance with the compounding ratios shown in Table 1 (tables 1-1 and 1-2), and the adhesive compositions were dissolved and mixed in toluene to prepare coating liquids. A primer (a solid content 5% by mass toluene solution obtained by mixing polymethyl methacrylate grafted natural rubber (trade name "MG30" manufactured by Missina rubber research Co., ltd.) and cyclized rubber (trade name "ALPEX CK-450" manufactured by UCB Japan Co., ltd.) in a mass ratio of 3:1) was applied to one surface of a substrate to form a unit area weight of 0.8.+ -. 0.4g/m ² After the primer layer of (a), the prepared coating liquid was applied so that the thickness of the adhesive layer after drying became 32 μm, and drying and crosslinking were performed at 110 ℃.

The obtained adhesive tape was evaluated as follows.

(loss tangent)

An adhesive layer (thickness: 2 mm) for measurement was prepared using each adhesive composition. Then, the adhesive layer was punched out to have a diameter of 10mm, and this was fixed in a form of being sandwiched by parallel plates, and the obtained sample was used as a measurement sample.

The measured sample was subjected to dynamic viscoelasticity measurement under the following conditions using a dynamic viscoelasticity measurement apparatus, a temperature dependence graph of loss modulus (G ") and storage modulus (G ') was prepared, and minimum temperature, minimum value, maximum temperature, and maximum value were obtained from loss modulus (G")/storage modulus (G')=loss tangent (tan δ). In addition, as an evaluation, a case where the minimum side (minimum temperature of 78.7 ℃ or more and minimum value of 0.20 or less) and the maximum side (maximum temperature of 25 ℃ or less and maximum value of 1.15 or less) satisfy a predetermined range was designated as "Y", and a case where the minimum side and the maximum side do not satisfy "N".

The device comprises: manufactured by TA Instruments, trade name "ARESRDA-III"

Frequency: 10.0Hz

Temperature: -60-200 DEG C

Temperature rise: 10 ℃/min

Strain: 0.1%

(adhesive force)

Adhesive force was used according to JIS Z0237: 2000 test method.

As the adherend, PS (polystyrene), PP (polypropylene), PC (polycarbonate), roughened PC (matte-finished on one side, trade name "PCSP K6600" manufactured by takiron corporation), glass, SUS plate (SUS 304 plate polished to a uniform surface with #280 water-resistant polished paper), al plate, acrylic-based coated plate (SPCC-SB acrylic-based coated plate manufactured by japan iron corporation) (paint: japan paint "company, ltd., of japan, and the like")).

Since the adhesive force of the adhesive composition in this embodiment is preferably 2.0N/10mm or more and 8N/10mm or less, the adhesive force in this range is evaluated as "a" in the case where all adherends are present, the adhesive force in this range is evaluated as "B" in the case where 1 adherend is out of range but can maintain this range for other adherends, and the adhesive force in this range is evaluated as "C" in the case where 2 or more adherends are out of range.

(high temperature holding force)

The time until the falling of the weight was evaluated by adding a weight of 500g load in the vertical direction to the end of the test piece attached to the SUS plate in the longitudinal direction having a length of 25mm and a width of 10mm at the measurement temperature of 120 ℃. The drop time is 120 minutes or longer and is determined as "A", 60 minutes or longer and less than 120 minutes is determined as "B", and less than 60 minutes is determined as "C".

(contamination by adherends)

The adhesive tape was attached to each of the adherends used in the measurement of the adhesive force, and after the adhesive tape was left to stand at 65℃for 7 days or more in an atmosphere of 85% RH, the adhesive tape was left to stand at 5℃for 2 hours or more and cooled, and the adhesive tape was peeled from the adherend by hand in an atmosphere of 5℃to examine the presence or absence of residual adhesive and contamination on the adherend by visual observation.

The case where no trace or contamination of the adhesive tape was observed at all was determined as "a", the case where almost no trace or contamination of the adhesive tape was observed was determined as "B", and the case where trace or contamination of the adhesive tape was significantly remained was determined as "C".

(self-adhesive face adhesion)

The adhesive tape was attached to the adherend, the end was bent 5mm toward the adhesive surface, and the length of detachment of the bent end was measured visually after being left to stand for 1 day or more in an atmosphere of 85% RH at 65 ℃.

(comprehensive evaluation)

In all the evaluations, the case where the rank a and the rank B are 2 or less was evaluated as "a", the case where the rank a and the rank B are 3 or 4 was evaluated as "B", the case where the rank a and the rank B are 5 was evaluated as "C", and the case where the rank D is included as "D".

[ Table 1-1]

[ tables 1-2]

[ Table 2-1]

[ Table 2-2]

Evaluation results

As shown in tables 1-1 and 1-2, compositions satisfying the loss tangent specified in the present invention were obtained in examples, and compositions satisfying either or both of the minimum side and the maximum side were not obtained in comparative examples.

As shown in table 2-1, the adhesive tapes of examples 1 to 9 were excellent in all of adhesive force, high-temperature holding power, contamination by adherends, and self-adhesive surface adhesion.

On the other hand, in comparative examples 1,2 and 7 to 12, as shown in Table 2-2, the adhesive force was excellent but the high temperature holding power was poor. Comparative examples 3 and 4 were excellent in high-temperature retention but poor in adhesive force. The adhesive force and the high temperature holding force of comparative examples 5 and 6 were poor. In addition, in any of the comparative examples, the contamination of the adherend was rated D, and the versatility was low.

Industrial applicability

The pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape for temporary fixation, which has excellent adhesive strength to various adherends (articles) and exhibits low contamination, and thus has high versatility.

Description of the reference numerals

11. 21: substrate material

12. 22, 23: adhesive layer

Claims

1. An adhesive composition comprising a natural rubber, a crosslinking agent, a tackifier and a crosslinking regulator,

the adhesive composition contains, as the crosslinking agent, 2.5 to 10 parts by mass of an isocyanate compound having a diphenylmethane diisocyanate structure per 100 parts by mass of the natural rubber,

the adhesive composition contains 60 to 90 parts by mass of a petroleum-based adhesive agent having a softening point of 125 ℃ or higher per 100 parts by mass of natural rubber,

the crosslinking regulator is at least one compound selected from hindered phenol compounds, phosphorus compounds, metal compounds, benzotriazole compounds, triazine compounds and hindered amine compounds,

the adhesive composition contains 1 to 5 parts by mass of the crosslinking regulator relative to 100 parts by mass of the natural rubber,

the adhesive composition has a minimum loss tangent temperature of 78.7 ℃ or higher and a minimum value of 0.20 or lower after curing, and a maximum loss tangent temperature of 25.0 ℃ or lower and a maximum value of 1.15 or lower.

2. The adhesive composition of claim 1, wherein the natural rubber has a mooney viscosity ML at 100 ℃ ₁₊₄ 20 to 85.

3. The adhesive composition of claim 2, wherein the natural rubber has a mooney viscosity ML at 100 ℃ ₁₊₄ 20 to 35.

4. An adhesive tape comprising an adhesive layer comprising the adhesive composition according to any one of claims 1 to 3 on at least one surface of a sheet-like substrate.